Selective catalytic reduction (“SCR”) exhaust aftertreatment systems are an important technology for reducing NOx emissions from internal combustion engines such as diesel engines. SCR systems generally include a source of urea solution, a pump unit for pressurizing the urea solution, a metering unit for providing a controlled amount or rate of urea solution to an SCR catalyst, and an injector which provides urea solution to a urea decomposition region of an exhaust flowpath located upstream from an SCR catalyst. Many SCR systems also utilize pressurized gas to assist the flow of urea solution to the injector. While providing important reductions in NOx emissions, SCR systems suffer from a number of shortcomings and problems. Use of urea solutions in SCR systems may result in growth of urea crystals or deposits on various components of the system which may disrupt their operation. Injector nozzles may become blocked due to formation of urea deposits when urea solution is exposed to elevated temperatures. Such deposits may also form on the SCR catalyst or other components located in the exhaust flowpath or otherwise exposed to high temperatures. Leakage of urea to the ambient environment can damage or destroy other system components. There is a long felt need for advancements mitigating these and other shortcomings associated with SCR systems utilizing urea solution.